Hey there. Thought I'd just give you a bit of input on the Garchomp code since you were so kind enough to give me a spare Hoopa even though you didn't really need an extra code at the moment.
So this is currently my trade history with others:
Traded 3 Garchomp codes in return for a NA Play! Mewtwo Code. This was probably too much by 1 code (normal rate is 2 codes for 1 NA Mewtwo code) but this is probably the amount you'll require to get hold of one of those elusive codes. No one seems to want to let go of their Mewtwo codes at the moment. Even if you were to offer two codes, you're still quite unlikely to get hold of a Mewtwo code in return.
Traded 1 Garchomp code in return for a Pokemon Cafe Pikachu code. This was probably way too much for such a code as the user I obtained it from got the said Pikachu code from the previous user for a mere NA Arceus code. He probably got really lucky but just keep in mind that you can get more than a Pikachu code with this code.
As for the other rates I've seen so far:
1 Garchomp code= 7 Arceus code This is the normal rate apparently. However just a few hours ago, I saw someone obtain 10 codes in exchange for just one of them. So you may be able to obtain more than 7 if you get really lucky.
1 Garchomp code is also equal to 10 NA Darkrai codes I think. This is something I am not too sure of so you'll have to see for yourself. That's about all the rates I know for these codes. Here's a link to a recent thread which is looking for Garchomp codes. There might be Pokemon of interest for you there.
Also another heads up but I am pretty sure you're already aware of this since you've been here for so much longer than me. These codes are going to decrease in value as time passes (it's the same with any code of course) so if you plan on getting them exchanged for something else, it's best to do so as soon as possible.
That's all I wanted to say. Thank you again for such a wonderful trade.